Apparatus for evaporating liquids



Feb.: 16, .1932. R1 N. EHRHART APPARATUS FOR EVAPORATING LIQUIDS Filed June 2, 1927 INVENT ,fiw'

o 0 0 o o o o o o 0 0 0 0 0 o 0 o o o O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o o o o o o 0 o 0 0 0 0 0 o 0 0 0 0 0 o 0 0 o o 0 0 0 0 o 0 0 o o o 0 0 o o o 0 8 o o 0 0 o o o o o o o o o o o o o o o o o o o o o o o o Patented Feb. 16, 1932 STATES earner RAYMOND N. EHRHAR-T, F EDGEWOOD, PENNSYLVANIA, ASSIGNOR TO ELLIOTT COM- PANEL, 6F PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA APPARATUS FOR EV jfORiTIl l' G LIQUIDS Application filed. June 2, 1927. Serial No. 195,924.

The present invention relates broadly to the exchanging of heat in connection with the treatment of liquid, and more particularly to an improved apparatus by means of which such a heat exchange is effective for the evaporation of at least a portionof the liquid being treated.

In the art to which the present invention relates, it is customary practice to utilize 10 high pressure steam for the development of energy in mechanical or other forms, the steam in passing through the particular apparatus provided for that purpose, giving up a certain portion of its thermal energy. This portion of the thermal energy so given up is in turn transformed by the apparatus provided into mechanical energy for example, capable of being conveniently utilized. In such cases, however, the greater portion of 2b the thermal energy of the steam is not utilized by the apparatus with the result that the steam rejected thereby carries away with it a greater portion by far of its original thermal energy than was used in such appara- 2 tus. In other words, the thermal energy in the exhaust of standard apparatus, such, for example, as a steam engine, is manytimes that which has been utilized by the engine. The thermal energy content of exhaust steam so in such cases is usually referred to as degraded or lower level heat.

In the operation of apparatus utilizing steam, itis necessary in order to obtain the a maximum range in the utilization of heat, to insure exhausting of the apparatus into a region having the lowest practical pressure. Conveniently such a condition of low pressure is produced by means of a condenser, the temperature maintained thereby usually be- 4 ing so low, however, that there is no way of utilizing all of the low level heat in the range as maintained by the condenser. It is, however, possible to utilize small portions of the low level heat that would be ordinarily re- 1 jected to the condenser, and it is with this phase of the operation that the present invention deals.

One of the objects of the present invention, therefore, is to effect a practical utilization 59 of a portion of the degraded heat for evaporating, and more particularly that portion which is ordinarily thrown away.

In my copending application Serial No. 113,428, filed June 3, 1926, there is disclosed and claimed one method and apparatus by means of which extremely desirable results in this connection may be obtained. I have found, however, that it is possible to further.

which the invention may be carried out and a portion of the low-level heat effectively utilized. Y

In carrying out the present invention there may be provided a main condenser 2 having a header at one end divided by a transverse partition 3, whereby cooling water delivered to the condenser through a suitable connection l passes through the tubes 5 in the lower portion of the condenser in one direction and then by means of the header (not shown) at the opposite end of the condenser is returned through thetubes 6 in the upper portion thereof in the other direction. After having absorbed a certain amount of heat from the vapor delivered to the condenser through a suitable vapor inlet 7, the main body of the cooling water is discharged from the condenser through a suitable ofitake 8, and led to any desired point.

Usually all of the heat in the exhaust steam delivered through the vapor inlet is communicated to the cooling water which in turn goes to waste. In accordance with the presout invention, at least a portion of the heat which is thus normally wasted is conserved by the utilization thereof for the production of temperature conditions such that a sufiicient quantity of raw water may be evaporated. for example, to make up the losses in distilled water incident to normal power plant operation. Such desirable results may be accomplished by the provision of relatively large and relatively small tube nests which are suitably confined, and by so utilizing the vapor as to cause that portion of the water passing through a relatively small tube nest to be raised above the temperature of the main body of cooling water passing through a relatively large tube nest. -his may be accomplished y the provision of the different tube nests within a common casing, or as disclosed in my co-pen ding application, Serial No. 195,925 filed June 2, 1927, may be accomplished by the provision of separate tube nests, each with its own confining casing.

In accordance with the present form of my invention, there is provided in the water box above the tube nest 6 a partition which constitutes an efiective division between the nests and G which are relatively large tube nests, and nests 10 and 11 which are relatively small tube nests. That portion of the cooling water which is not discharged through the ofltake 8 may pass upwardly in any desired manner as for example, through a connection 12 controlled by valve 13. lVith the valve 13 open, this portion of the cooling water JHSSGS through a connection 14 to the tubes 10, through which it flows to the opposite end of the condenser. It is then returned through the tubes 11. which discharge into a supplemental water i'ftal-ie It. It will he apparent that the tube nests 10 and 11 are so located as to be directly exposed to steam entering the main condenser through the inlet 7. It is usually found that tubes first facing the inner flow have the highest heat transfer and those farthest removed from the vapor flew, the lowest heat transfer.

Under such conditions, the tubes in nests 10 and 11 will have a more eflicient heat trans for than the tubes in any other part of the condenser. selecting proper water quantitics and flow velocities through the respective tube nests, I can obtain such an eflicient transfer of heat from the vapor to the water passin therethrough that the water leaving through the supplemental connection 14 will have a temperature almost equal. to that of the temperature of the vapor delivered to the condenser. In other words, I pre'terablfi-v so proportion the entire condenser that the temperature of that portion of the water delivered through the inlet 1% and leaving through the supplemental outlet 143 is almost equal to the temperature oi the steam.

I also preferably provide a second conden referrer er 15 which will hereinafter supplied vapor. the 9th vacuum condo; operates to maiuta'n a vacuum which i high as possible within practicable limits. 1 his vacuum in all cases must be greater than the vacuum maintained by the main condenser.

I have found that it is possible to so proportion the high vacuum condenser in regard to surface, water circulation and the like, that it is practically possible to always maintain a vacuum, the incident steam temperature of which is from 10 to 15 lower than that of the co-incident vacuum in the main condenser.

For purposes of illustration only, it may be pointed out that in ordinary operation, a main condenser of the general character herein disclosed might be supplied with cooling water at a temperature of F., which water will be raised to a temperature of approximately 65 F., and discharged at this temperature from the condenser. Under such conditions, a steam tenn icrature of 75 might be maintained in the steam inlet of the condenser. ll ith a condenser constructed as herein referred to. this would result in the production in the comparatively small quantity of water flowing through the relatively small tube nests of a temperature of approximately 73 E, which tcn'iperature closely approximates that of the supplied steam. lVith the temperature conditions as referred to in this example, the high vacuum con denser might be so proportioned that with the same temperature of cooling water, it would have a discharge temperature of F., thereby maintaining a vacuum such that the steam temperature at its inlet 16 would correspond to F. The foregoing values are not given as representing the absolute performance of such an apparatus, but are merely tvpical of the general temperature range that it is sometimes desirable to ohtain, and which may be obtained and maintained with an apparatus of the general nature herein d sclosed. If the apparatus is so operated that the high vacuum condenser maintains a steam temperature of 60 and the auxiliary tube nests deliver water at a temperature of approximately 73. there will be a temperature gradient of 13 between the temperature of the water passing through the supplemental outlet 14? and the temperature in the inlet 16 of the high vacuum condenser. This temperature gradient may be verv effectively utilized for the evaporation by flashing of a portion of the water passing through the supplemental outlet. such flashing being obtained at the expense of the cou taincd heat in such portion of the water.

lVhere flashing of such nature is desired. there conveniently provided a flash chamber 17 having its vapor space operativcly connected to the inlet 16 ot' the high vacuum condenser, and constructed. to receive water from the auxiliary tube nests of the main condenser through the supplemental outlet 14 Under such conditions, the water entering the flash chamber will immediately boil violently due to its excess heat above the natural boiling temperature of maintained in the flash chamber by the high vacuum condenser. A certain portion will consequently be carried over into the high vacuum condenser wherein condensation will occur to change the same from its vapor phase to its liquid phase as distilled water. This distilled water may in turn beconveyed to any desired point for use. If desired, it may be returned to the hot well 18 of the main condenser through a manometric loop The cooling water discharged from the high vacuum condenser may be delivered to any desired point, but conveniently it is delivered to the same point as that to which the main portion of the cooling water from the main condenser is discharged.

In accordance with the disclosure of my co-pending application, Serial No. 113,428 hereinbefore referred to, it has been proposed to effect removal of the water from the flash chamber 17 and deliver it to some suitable point for re-use or for disposal. It will be apparent to those skilled'in the art that if there were only a 10 flash gradient in the evaporating chamber 17, approximately 100 times as much water would be passed through the evaporator as would be evaporated therein. Therefore, if the apparatus is of such construction as to effect the evaporation of 10,000 pounds of water per hour with a 10 flash gradient, there must obviously, under such conditions, be approximately 1,000,000 pounds per hour of raw water circulated through the evaporator. This means that the amount of air incident to 1,000,000 pounds .of water is necessarily liberated in the flash chamber and all of the air released therein necessarily passes through the connection 16 to the high vacuum condenser which is thus called upon. to handle the same in addition to the steam load represented by the steam disd therewith. This has heretofore necy so interfered with the e'liiciency of the high vacuum condenser as to require the same to be abnormally large relative to the amount of steam condensed. As a matter of fact, in accordance with prior practice, in view of the desirability of maintaining the highest possible order of vacuum in the high vacuum condenser, there has previously been supplied thereto a very liberal amount of cooling water through a connection 20, this water being subsequently disc iarged through a suitable offtake 2 Also, such condenser has heretofore ordinarily been equipped with gas exhausting means of great capacity, such for ex ample as a multistage ejector well understood in the art. In accordance with the present invention, it is possible to replace such multi-stage ejector with a single-stage ejector 22 as herein disclosed although obviously the utility of the invention is not limited with respect to the construction, arrangementor efficiency of the ejecting means actually utilized. 0

The increased efficiency contemplated by the present invention is effected by novel disposition of the water withdrawn from the flash chamberl'l', which water instead of being thrown away or delivered for example to the hot well of the main condenser, is sup jected to repeated re-circulation through the the flow of water through the re-circulating connection and into the pipe 14 leading to the tube nest 10 may be controlled. Such recirculation would necessarily result, at least after a comparatively few number of cycles in the elimination of at least the major portion of all of the air contained therein so that thereafter the surface of the condenser 15 could be greatly diminished as well as the size and consequent steam consumption of the ejecting means 22.

It is equally as obvious, however, that some makeup must necessarily be supplied to the flash chamber under such conditions inasmuch as a certain amount is removed during each cycle in the form of vapor produced by the evaporation therein. In order to keep the system primed, and to maintain a substantially constant body of water therein, there would necessarily be supplied thereto an amount equivalent at least to that evaporated. In other words, if the apparatus was started into operation with a certain water level, and 10,000 pounds per hour was removed by way of evaporation, there would necessarily be supplied at least 10,000 pounds per hour as make-up, and when the outfit came into actual operation under the re-circulating conditions referred to, the only air to be removed and consequently the only air to be handled by the high vacuum condenser would be that resulting from air infiltration plus the comparatively small amount coming in with the makeup water.

A re-circulation of all of the water from the flashing chamber would result in still another difiiculty represented by the concentration therein of the salts and other soluble solids carried by. the water. In order to obviate such a condition, it is necessary to provide means for keeping down such concentration, and this may be conveniently accomplished by the provision of an overflow connection 26 connected at any desired point in the re-circulation system and effective through the control valve 27 for controlling iii) the amount of water which is permitted to pass at any given time to over flow or waste. By thus continuously Withdrawing a certain portion of the water, the objectionable concentration referred to may be overcome. Such an operation, however, necessarily requires the provision of some means for controlling the supply of water to the apparatus in such manner that not only is the additional amount of makeup supplied automatically but also an additional amount represented by that passing through the overflow connection. Such a control may conveniently be eiiected by the provision of a float 28 in the flash chamber and connected to a valve 29 in a supplemental water inlet 30. This inlet 30 may communicate with an outside source of water, or may, and preferably does, communicate directly with the oiitake 8 from the main condenser whereby only heated water is supplied for makeup purposes. The float is conveniently originally adjusted in such manner as to continuously admit a greater amount of li uid than that evaporated, and preferably istantially twice such amount, it having been found advantageous to pa to overflow substantially as much liquid durmg each recirculation cycle as is evaporated by reason of such cycle.

By the use of the present invention, I have found it possible to substantially cut the size of the high vacuum condenser 15 in half, and to operate the ejecting means 22 with approximately 1/50th of the amount of steam required for normal operation under conditions in which no portion of the water from the flash chamber is re-eirculated.

It will be apparent that with the re-circulating connection herein disclosed, the con nection 12 with its controlling valv is not essential and may be omitted if desired. In starting the apparatus into operation, however, the valve 13 may be left open to insure passage of water to the tube nests 10 and 11. Also, in the event of temporary shut down of the re-circulating pump, the connection 12 may be utilized to keep the apparatus in operation.

From the foregoing it will be apparent that I have provided an improved method and apparatus by means of which raw water is evaporated by low level or degraded heat represented by the vapor introduced into the main condenser, and that recovery is eflected under such conditions that the size of the units required and the amount of steam utilized is kept as low as possible. Certain advantages of the invention arise from the pro vision of apparatus by means of which such a recovery can be effected.

Still further advantages arise from the combination of a flash chamber receiving water heated by low level heat at substantially the temperature of the exhaust steam, and having a reduced size made possible by a recirculation in a novel manner of the unevaporated portion of the water in the flash chamber.

I claim:

1. Evaporating apparatus, comprising a main condenser, auxiliary heating tubes within said condenser and subjected to the pressure conditions therein, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, and means for re-circulating at least part of such portion of cooling water through said tubes.

2. Evaporating apparatus, comprising a. main condenser, auxiliary heating tubes within said condenser and subjected to the pressure conditions therein, a common source of cooling Water supply for the main condenser and for said auxiliary heating tubes, and means for continuously re-circulating a portion oi said supply through said auxiliary heating tubes.

3. ltvaporating apparatus, comprising a main condenser, auxiliary heating tubes within said condenser and subjected to the pressure conditions therein, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, at flash chamber, means for delivering water from said auxiliary tubes to the flash chamber, means for maintaining in said flash chamber a pressure lower than the pressure in the vapor space of said condenser, and means for re-circulating Water from the said flash chamber through said heating tubes.

4. Evaporating apparatus, comprising a main condenser having a water outlet, auxiliary heating tubes in said condenser, a flash chamber. means for delivering water to said auxiliary tubes, means for delivering water from said auxiliary tubes to the flash chamber, means for re-circulating water from the flash chamber through said tubes and means for supplying make up water from said outlet to maintain the desired amount during recirculation.

5. Evaporating apparatus. comprising a main condenser, having an outlet, auxiliary heating tubes cooperating with said condenser, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such, portion of cooling water through said tubes, and means for adding to said recirculated water additional water from said outlet.

6. Evaporatiug apparatus, comprising a main condenser, auxiliary heating tubes cooperating therewith. means tor passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least partof such portion of cooling water through said tubes, means for preventing solid concentration in the recirculated water, and means for maintaining the quantity of recirculated water substantially constant.

7. Evaporating apparatus, comprising a main condenser, auxiliary heating tubes cooperating therewith, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such portion of cooling water through said tubes, means for preventing solid concentration in the recirculated water, and means for maintaining the quantity of recirculated water substantially constant by supplying thereto cooling water from said main condenser.

8. Evaporating apparatus, comprising a main condenser, auxiliary heating tubes therein, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such portion ofcooling water through said tubes, means for withdrawing a portion of such recirculated water to prevent solid concentration, and means for making up the amount of water so withdrawn.

9. Evaporating apparatus, comprising a main condenser, auxiliary heating tubes within said condenser and cooperating therewith, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such portion of cooling water throughsaid tubes, a flash chamber cooperating with said recirculating means, and a separate condenser communicating with said flash chamber for withdrawing vapor therefrom.

10. Evaporating apparatus, comprising a main condenser, having an outlet, auxiliary heating tubes cooperating with said condenser, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such portion of cooling water through said tubes, means for adding to said recirculated water additional water from said outlet, and means responsive to the water being recirculated for controlling the amount of water added.

11. Evaporating apparatus, comprising a main condenser, having an outlet, auxiliary heating tubes cooperating with said condenser, means for passing a portion of the cooling water for said condenser through said auxiliary tubes, means for recirculating at least part of such portion of cooling water through said tubes, means for adding to said recirculated water additional water from said outlet, and float operated means responsive to the water being recirculated for controlling the amount of water added.

In testimony whereof I have hereunto set my hand.

RAYMOND N. EHRHART. 

